No matter how simple the job, make sure you get at least three estimates for it.
For bigger or more complex jobs do not be discouraged by the first high estimate you receive. No need to panic!
Make sure the contractor is licensed, insured, and bonded.
Ask for referrals to make sure that the contractor’s previous projects were satisfactory to the customers.
Make sure the details of the work and the timeline are explicitly detailed in your contract.
Make sure the contractor has obtained the right permits (when necessary) before they start the job.